Small pneumatic cylinders are utilized in many industries for performing and controlling numerous operations. These pneumatic cylinders are conventionally of relatively small diameter, such as 21/2 inches or less. Since these cylinders are often used for controlling a specific operation, such that the control and performance of this operation in an accurate manner is the most critical feature, relatively small cylinders can thus be successfully utilized.
At the present time, many of the utilized pneumatic cylinders are of the nonbumpered type, that is, the piston does not have any bumpers thereon so that the piston thus impacts against one or both end caps of the cylinder housing during the reciprocating movement thereof. This produces a hammering action which often emits an undesirably loud noise. This hammering action can be particularly severe and undesirable in those situations where the cylinder is repetitively cycled at a relatively rapid rate. The noise emitted by the hammering of the piston on the cylinder housing is obviously annoying, and can create a possible health hazard, to any personnel who may be working in the immediate vicinity.
In view of the noise associated with such nonbumpered cylinders, an increasing number of users of such cylinders now require that the cylinders have resilient bumpers for preventing the metal-to-metal contact between the piston and the cylinder end caps. While many bumpered cylinders are presently available, nevertheless these known bumpered cylinders create additional disadvantages.
Specifically, when bumpers are added to the cylinder, then this results in the length of the piston being increased when the bumpers are mounted thereon, or conversely results in the internal length of the cylinder housing being decreased when the bumpers are mounted on the end caps. The presence of the bumpers thus causes the cylinder stroke to be reduced in contrast to the stroke of an equivalent nonbumpered cylinder. Accordingly, to provide the bumpered cylinder with a stroke equal to that of a nonbumpered cylinder, it is necessary to utilize different components in the manufacture of the bumpered and nonbumpered cylinders so as to result in the same stroke. For example, if identical pistons are utilized, then a bumpered cylinder requires the use of a longer housing sleeve and a longer piston rod in order to result in the same stroke length as an equivalent nonbumpered cylinder. Alternately, pistons of different length may be used for bumpered and nonbumpered cylinders to enable use of the same housing. These possibilities are obviously undesirable since the manufacturer must thus stock different sizes of components, specifically rods and housing or pistons, in order to provide finished cylinder assemblies either with or without bumpers while having the same stroke.
A further disadvantage of this structure is that the completed bumpered cylinder assembly has an overall length which is slightly greater than the overall length of a nonbumpered cylinder assembly of the same stroke. This creates a significant problem for users who wish to replace an existing nonbumpered cylinder with a bumpered cylinder of the same stroke length, or vice versa, since the difference in the overall length of the bumpered and nonbumpered cylinder assemblies (for the same stroke) thus requires that the cylinder mounting structure be modified to accommodate the different length cylinder. In many situations, modifying the mounting so as to accommodate the different length cylinder is a laborious and time consuming, and hence expensive, operation.
Accordingly, it is an object of the present invention to provide an improved fluid pressure cylinder, and in particular a small diameter pneumatic cylinder, which can be manufactured either as a bumpered or nonbumpered cylinder while effectively overcoming the disadvantages mentioned above. More specifically, it is an object of this invention to provide an improved cylinder which utilizes standardized or universal parts so as to permit the cylinder to be provided with or without bumpers, with the resulting assembled cylinder whether provided with or without bumpers (1) being of the same overall length and possessing the same stroke and (2) having a physical size that is smaller or the same as comparable and equivalent nonbumpered cylinder.
Another object of this invention is to provide an improved fluid pressure cylinder, as aforesaid, which utilizes a standardized housing, piston and piston rod for forming a cylinder either with or without bumpers, which bumpers can optionally be positioned on the piston when desired, with the overall assembled length and piston stroke of the cylinder being identical whether provided with or without bumpers. In accomplishing this object, the piston is selectively mounted on the piston rod in one axial orientation if bumpers are not being utilized, and the piston is reversed and mounted on the piston rod in the opposite axial orientation when bumpers are being utilized.
A further object of the present invention is to provide an improved cylinder, as aforesaid, which provides different cooperating pairs of stops between the piston and the housing, depending upon whether the cylinder is of the bumpered or nonbumpered type, so as to permit the same identical housing structure to be utilized for both bumpered and nonbumpered operations while still maintaining the same stroke length for the piston.
Still a further object of this invention is to provide an improved cylinder, as aforesaid, which permits the use of a minimum number of different components for manufacturing both bumpered and nonbumpered cylinders, and which permits the users of such cylinders to readily interchange bumpered cylinders for nonbumpered cylinders, and vice versa, without effecting the desired stroke length and without requiring the cylinder mounting structure to be modified.
Another object of this invention is to provide an improved cylinder, as aforesaid, which provides the added option of permitting a permanent magnet to be easily mounted on the piston so as to cooperate with an external proximity switch to thereby readily indicate piston position, without requiring any substantial modification or rearrangement of the pressure cylinder while still retaining complete standardization of cylinder components and without affecting the desired stroke length.
Other objects and purposes of the invention will be apparent from reading the following description and inspecting the accompanying drawings.